U.S. Pat. No. 4,289,278 shows two different powder spraycoating devices of this kind wherein an annularly slotted compressed-air outlet issues into the powder duct upstream and/or downstream of a support-offset for a high-voltage electrode. The coating powder is sprayed by means of flow detachment at the end of the powder duct and/or by means of a funnel-shaped duct mouth and/or by a deflector or baffle configured at the center of the powder flow downstream of the powder duct. Said baffle may be fitted with one or more high-voltage electrodes to electrostatically charge the coating powder, whereas an electrode situated in the air flow from the compressed air outlet is grounded, as a result of which unipolar corona discharge takes place from the high-voltage electrode to the grounded electrode.
The German patent document 195 42 863 A1 shows a powder spraycoating device comprising a grounded electrode configured centrally in the powder flow and further downstream from said electrode high-voltage electrodes that inwardly project from the powder duct wall. The electrodes may be configured in an airflow in order to avoid having powder particles deposit on them. The European patent document 1 008 392 A2 shows a powder spraycoating device comprising a powder duct receiving an elongated central body in its downstream end zone, said body's downstream end segment flaring in funnel-like manner and together with the powder duct wall subtending a cross-sectionally annular powder duct segment. Compressed air is introduced into the powder duct, in particular into the cross-sectionally annular powder-duct segment, to generate compressed-air and powder eddies swirling around the central body.